The changes of epidermal calcium gradient and transitional cells after prolonged occlusion following tape stripping in the murine epidermis

Disruption of the epidermal permeability barrier causes an immediate loss o f the calcium gradient, and barrier recovery is parallel with the restorati on of the calcium gradient in the epidermis, Artificial restoration of the barrier function by occlusion with a water vapor-impermeable membrane abrog ate the expected increase in lipid synthesis and retard the barrier recover y, as well as block the normalization of the epidermal calcium gradient. To clarify the long-term effects of occlusion after acute barrier perturbatio n, we studied the calcium distribution and epidermal keratinocytes response after occlusion with a water vapor-impermeable membrane immediately follow ing tape stripping in the murine epidermis. Acute barrier disruption caused an immediate depletion of most calcium ions in the upper epidermis, oblite rating the normal calcium gradient. When the skin barrier function was arti ficially corrected by occlusion, the return of calcium ions to the epidermi s was blocked. After 2 h of air exposure or occlusion, the density of epide rmal calcium precipitates remained negligible. The transitional cell layers appeared with occlusion, but not or negligibly with air exposure. By 6 h t hough, calcium precipitates could be seen, the density of the calcium preci pitates with occlusion was more sparse than with air exposure, With the air exposure, the thickness of the stratum corneum had normalized and the calc ium gradient nearly recovered to normal after 24 h. The longer the occlusio n period, the greater was the increase of transitional cells. By 60 h of oc clusion, the thickness of the stratum corneum had increased and the transit ional cell layers had disappeared, in parallel with the calcium gradient wh ich was almost normalized. These results show that prolonged occlusion of t ape-stripped epidermis induced transitional cells and delayed the restorati on of the epidermal calcium gradient, the stratum corneum was then restored , transitional cells having disappeared, in parallel with normalization of the epidermal calcium gradient.